Process for the determination of melting temperatures of materials and apparatus for carrying out the aforesaid process



Jan. 13, 1931. E GRAAF 1,789,098

PROCESS FOR THE DETERMINATION OF MELTING TEMPERATURES OF MATERIALS ANDAPPARATUS FOR SARRYING OUT THE AFORESAID PROCESS Filed Jan 2'7. 3Sheets-Sheet 1 IdVENTOR GERRI'T A.

e GRAAF (deceased) ATTORNELS Jan. 13, 1931. 5,. DE GRAAF 1,789,098

PROCESS FOR THE DETERMINATION OF MELTING TEMPERA'WRES 0F IATERIALS ANDAPPARATUS FOR CARRYING OUT THE AFORESAID raocmss 3 Sheets-Sheet 2 FiledJan. 27, 1928 'naunnanan nvvmron- GERRLT A.de GRAAF (deceased) ATTORNEY$1,789,098 KPERATURES OF MATERIALS THE AFORESAID raocnss Jan. 13, 1931.G. A. DE GRAAF PROCESS FOR THE DETERMINATION OF MELTING TE AND APPARATUSFOR CARRYING OUT Fil ed Jan. 27, 1928 3 Sheets-Sheet 3 Q E I m n. R m aN w v E e V w A A R G \N m A u R \1 m m fir m ll ATTORNEY? Patented Jan.13, 1931 AES GER-BIT A; DE GRAAF, DECEASED, LA'rE 0F BLOOMFIELD, NEWJERSEY, BY LEA FRANK DE GRAAF, EXEGUTRIX, or BLOOMFIELD, NEW JERSEY,assrenon T0 Emma & AMEND, OF NEW YORK, 1v. A CORPORATION OF NEW YORKPROCESS FOR THE DETERMINATION OF MELTINGTEMPERATURESOE IMATERIALS ANDAPPARATUS .FOR CARRYING OUT THE LAFQRESAID EROGESS Application filedJanuary 27, 1928.

This invention relates to a process for the determination of the meltingor fusing .temperatures of material and to apparatus for carrying outthe aforesaid processes, and more particularly to a process ofdetermining the melting or fusing temperature of coal ash and to anautomatic instrument for effecting the said determinations.

The invention has many applications but in this specification it will bedescribed in connection with the determination of the melting or fusingtemperature of coal ash. This determination has a very importanteconomic and industrial importance and must be made with considerableaccuracy.

In the sale of coal, for example, the purchaser buys the coal on thebasis that the coal ash is only present to a certain amount and has acertain fusing temperature. The seller of the coal agrees, among otherthings, that if the ash fuses below a certain temperature he willreimburse the purchaser a certain amount of money depending upon thedifference in degrees of temperature between the contracted fusingtemperature and the actual fusing tei'nperature of the coal ash. At thepresent time the seller of coaloften has to make enormousreimbursementsto the purchaser because of the difference between the contracted andthe actual fusion temperatures. As the margin of prefit in selling coalto large consumers, such as public utilities, is very small, the selleris often subjected to serious losses. On the other hand, the purchaserof coal Who is operating a power plant, for instance, is vsubjected togreat trouble and expense if the coal contains an ash having ameltingtemperature lower than a' safe fusing temperature for which hecontracted. For example, in firing boilers troublesome clinkers form onthe grates. The clinker formation has many objections among which may bementioned the improper distribution of fuel over the grate surface, theformation of a more or less complete blanket over air openings andthrough the fuel bed, the interference with fuel movement on the grates,the clogging up of grate openings, andthe adherence of the clinker massto the stoker in such a way Serial No. 250,013.

that fresh fuel is pushed down by the lower ran and is caused to rideover the clinker mass on to the dumping grate where it is wasted. All ofthese objections, disadvantages, and troubles arise from the fact thatit is difficult to determine the fusing or melting temperatureaccurately by any commercial or practical method.

Heretofore, the most general method used and the one adopted by theAmerican Society for Testing Materials was the so-called cone method. Inthis method, as is well known, a representative sample of the ashcontained in the coal is mixed with a binder such as dextrine and isthen moulded into the form of a cone which has a height of 4 of an inchand base of an equilateral triangle having a side of of one inch. Thesecones afterbeing properly prepared are placed on a plate which issupported in a gas muffle furnace. After applying the heat for asufficient time in the furnace, an observer looking throughanobservation hole can see the cones begin to melt. Upon the fusion of thecone into a sphere the observer makes an observation of thetemperatureindicating pyrometer, either a thermocouple or an optical pyrometer, andrecords the temperature. This temperature is then arbitrarily consideredto be the softening or fusiontemperature of the ash. There areseveralerrorsinvolved in this temperature determination, the moreimportant of which are, first, that the thermocouple gives an inaccurateindication because it passes through and is heated by the flames of theburners which heat the muffle containing the cones; and second, that theatmosphere in the crucible is not truly reducing, and consequently, theiron contained in the ash is oxidized to a higher state of oxidationwith the liberation of heat within the cone itself. It is estimatedthatthe temperature measured and indicated by a thermo-couple pyrometer isin error by about C. A difference of this sort, however, may be veryimportant when considered from the economic point of View of a purchaseror seller of coal. In addition to the inaccuracy of the temperaturemeasurements by the same and different obiii servers, the cone method isa cumbersome and time-consuming procedure which' requires complicatedequipment.

Many attempts have been made to replace the present cone method with asatisfactory, reliable, accurate and practical method but nothing so farhas been successful.

carded, contemplated manual adjustments and operations for efiecting themelting or softening temperature of coal ash and for determining thetemperature at which the melting occurred. This method has manyobjections, the principal among which are that the manual operations donot give uniform heating, treatment and results; that two operators arerequired in order to make Fig. 1 is an elevational view, partly in.

section for purposes of clarity, of a preferred embodiment of theinvention; V

F ig. 2 is a sectional viewtaken on the line 22 of Fig. 1;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 is a sectional view taken on thev line T4 of Fig. 1;

F i9. 5 shows a fragmentary view, partly in elevation, of the rheostatused in my apparatus Fig. 6 illustrates a side elevation of theinstrument for melting the materials and for 'peratures actuates anautomatic rheostat R.

observin and measuring the melting tem- Fig. 7 is a diagrammaticillustration of the electrical connections; and

Fig. 8 depicts a modified cover used for.

covering the heating element of the instrument shown in Fig. 6.

Referring more particularly to Figs. 1 and 2, the letter M designatesv amotor which This rheostat controls electric current flowing throu htransformer T from supplyinglines L when switch S is turned on, toinstrument I. in order to make a compact structure capable of beinghandled asa unit, it is preferable to mount the motor, the switch,

the rhecstat and the transformer on a solid base B.

An electrical method which was proposed and dis- Within instrument I aheating element 1 constituted of platinum or tantalum for melting thematerials to be tested is incorporated. This heating element ispreferably held at its ends by clips 2 which may be integral with posts3. Any desired. way of mounting posts 3 on insulating foundation l maybe employed but the posts are herein shown as being-secured to thefoundation by means of threads 5. Rodsfi screw into or connect in someother suitable manner with posts 3 so that electricity can flow fromterminal connectors 7 to posts 3 and thus to heating element 1. In orderto establish a good electrical connection between the heating element 1and the post a clamping screw 8 is provided on each clip2.

The foundation 4 may constitute thebase of the instrument 1 or, as inthe illustration, may be joined to a metal framel) by a plurality ofscrews 10 or the like. As

the foundation thas to withstand heat as well as electricity it ispreferably made of a material such as asbestos wood or the like. Cut orotherwise formed in foundation 4 is a channel 11 for receiving arefractory cover 12 which has a transparent window 13 provided in itsupper face. Between the lower edge of cover 12 and the bottom of .thechannel, a gasket '14 is provided so as to maintain a gas-tight joint.In practice it is desirable to inake'the cover 12 of high-temperatureglass (e. g. pyrex lass) and to protect the glass with a metal shell 15having an opening for window 13. v

When a material is being tested that should be protected againstoxidation, the air trapped under cover 12 is witln'lrawn through channel16, connection 1", and tube 18 leading toan evacuating pump (not shown).Any suitable pump which gives a practically perfect vacuum may beemployed as one skilled in the art will readily understand. In order tomeasure the pressure existing in the space under cover 12, a channel 19leading to the said space is provided in foundation 4 which isconnected,

via inlet 20'and tube 21 to an absolute gauge 22. This gauge has a scale23 from which the pressures may be read directly. Of

course, neutral, reducing or other gases can be sucked into the spaceunderthe cover so that the heating andmelting operation can be conductedin any desired atmosphere.

Projecting upwardly-from metal frame 9 is an arm 24 which carries abranched bracket 25. This bracket has two sockets for mounting amonocular telescope magnifier 26 (e. g. a Carl Zeiss telescopicmagnifier) and a ra .diation pyrometer 27 known commercially asanfllrdometer. The magnifier 26 and the pyrometer 27 are mounted in thebracket at such. an angle to each other that their optical axes 28 and29 respectively intersect each other at about a point P on the heatingelement where the material to be tested is placed. On axis 29 and at thefocus of the radiation pyrometer, a thermo-element 30 is located. Allthe heat radiation received by the pyrometer is concentrated and focusedon thermo elemen't 30 which generates a small electric current. By passing the generated current to 'a 'galvanometer 31 via conductors 32 and33 the temperature existing at point P may be measured and indicated onscale This scale may be graduated in any suitable units, as forinstance, in degrees Fahrenheit. In order to be able to focus thepyrometer and the telescopic magnifier, each is provided with an eyelens and 36' respectively. I

Electricity is supplied to the heating element of instruments 1 throughconductors 37 and 38 which are connected respectively to the outletterminals 39 and 40 of the secondary side of transformer T. The primaryside of the transformer is connected to a binding post 11 at one end ofrheostat R by conductor 42 and to switch S by conductor The switch isalso provided with a connection llto main electrical supply lines Lwhereas the rheostat has a connection 45 extending from bindin post $6to a conductor 47 which leads to supply lines L.

The rheostat has the usual electrical connections in that binding post46 is united to the right end of helical resistance coil 18 by means ofring 19 and binding post 41 is electrically secured to the left end ofslide bar 50 (see Fig. 5). Mounted on the slide bar is a carriage 51which is provided with spring contact clips 52. These clips bear againstthe turns of the resistance coil and thus establish a connection betweenthe slide bar and the resistance coil (see Fig. l). The upper part ofthe carriagehas a member 53 slidably positioned on a rotatable helicallythreaded rod 51. 'By providing a pin clutch 55 of well 'knownconstruction, the member 53 and thus'the carriage 51 may be eithercoupled With or uncoupled from rod 5%. lVhen the pin 56 of clutch is inmesh with the threads of rod 54: as shown in Fig. 4, the carriage iscoupled with rod 54. By pulling the pin out and turning it 90 across lug57, it bears against the face of member and thus maintains an uncoupledcondition between the carriage and the rod. In this condition thecarriage may be moved back and forth on the slide bar.

Thethreads on rod 54 may be of any particular type but I have found thatit is preferable to make the pitch of the threads on the right handportion of the rod about one half of the pitch of the threads on theleft hand portion. This means that it will take about twice as long forthe carriage to move across the'right portion of the rheostat as it willto move across the left portion placed in a small agate mortar.

of the rheostat. In order to provide for the rotation of the rod it isappropriately mounted in plates 58 which are suitably attached to thesides-of the rheostat and it has a gear wheel 59 secured to one endherein shown as the right end. The gear Wheel 59 is driven by a wormgear 60 on motor M which is electrically connected to supply lines L viaconductors 47 and 61. By selecting a motor having a suitable speed andby using a worm and gear having appropriate construction, as one skilledin the art understands, the rod may be rotated at a speed sufiicient tomove the carriage across the right slde of the rheostat in about five tosiX minutes and across the left side in about three minutes.

The electrical connections for the motor and .for the transformerrheostat and heating element may be of any appropriate arrangement. InFig. 7 a diagrammatic illustration of a preferred arrangement isdepicted. The supply lines L may be those 'of an ordinary light circuitof 110 volts or of any other suitable source of elec T10 current.Interposed between main supply lines L and circuit lines 100 and 101 isa switch 102. Conductors 103 and 10% lead from circuit lines 100 and 101respectively to motor M. The circuit line 100 is attached to one end ofthe primary side P of transformer T by conductor 105 and the othercircuit line 101 is connected to one end of rheostat R by conductor 106.The rheostat is provided with 'a movable slide 107 which has anelectrical connection 108 extending between it and the other end'of theprimary P. The secondary side Kof the transformer is connecteddirectlywith the heating element 1 of instrument I by means ofconductors 109 and 110. lVhen switch 102 is thrown in so as to connectsupply lines L with circuit lines 100 and 101, the motor is actuated andthe heating element is supplied with electrical energy. By thissimultaneous action the heater begins to heat and the slide begins tomove from the left end of the rheostat to the right end and thus cutsout the resistance of the rheostat and increases the electric currentflowing to the transformer to a maximum.

In the process of determining the melting or fusing temperature'of coalash a specimen of the ash resulting from either a proximate or anultimate analysis of a sample of coal weighing about one gram is firstSufficient water, about one or two drops, is added to the ash or otherrefractory material which is then rubbed for a few minutes with an agatepestle to break up any coarse particles. The mortar and its contents aredried with the pestle and when dry, the mass is loosened up by rubbingit with'the pestle. The material (ash or the like) to tan entiresurface.

be tested is then ready to be placed on the heating element in theinstrument I to determine its fusion point. With this mode of preparinga saiipleall the complicated and elaborate work required for the preparation of the sample in the cone method is eliminated. This savesconsiderable time, labor and money.

After the specimen of material is placed upon tac heating element asshown at P in Fig. 1, and the telescopic magnifier and the radiationpyrometer are focused on material P, the switch S is turned on so as tosupplyelectricity simultaneously to motor M and to the circuit includingthe transformer, the rheostat and the heating element. The motorimmediately begins to move carriage 51 on the rheostat from its initialposition at the left end of the rheostat where all of the resistance ofcoil 48 is in the circuit to the right end where'all of the resistanceis cut out of the circuit. I

lVhen an electric current of 110 voltsand 60 cycles is used in thesupply lines L, a

- transformer stepping down the voltage to 10 volts is employed, and aresistance of 10.8 ohms is used in the rheostat, a tempera ture of about900 F. Wlll be available in a heating element constituted of a platinumstrip 2 inches long, of an inch wide and 2/1000 of one inch thick whenthe carriage traverses about one half of its travel on the slide bar, i.e. when the carriage reaches the junction between the coarse and thefine threads. The time consumed in traversing one half of the slide baris approximately three minutes.

During the remainder of the travel of the carriage, the operatorobserves the material being heated on element 1 through the telescopicmagnifier 26. As the carriage nears the end of its travel sur'iicientelectricity has passed through the heating element to generateheatenough to cause softening of the material or specimen under test.Upon initial fusion of the specimen a white border appears around theedge of the specimen or pellet of ash. As the temperature increases theborder spreads over the surface of the pellet and finally covers theWhen the black spot disappears from the centerofthe pellet, the finalfusion is reached. Since ash has no true melting point, it is desirableto obtain "present method and apparatus completelv With the cone cover.The electric current generated in the thermo couple 30.by the heat istransmitted to the galvanometer so that the temperature of the pellet iscontinually and automatically being indicated. lVhen the operator firstobserves the appearance of the white border around the edge of thepellet, he looks at the galvanometer and notes the temperature. thespecimen through the magnifier and when thecblack spot disappears fromthe the cone method the time required to make one test is aboutthree tofour hours of laborlous hot and lnconvenient work. The

eliminates these disadvantages.

-When temperatures under about 2800 F. are to be measured, a strip ofplatinum is to be used for the heating element. whereas, whentemperatures over 2800" F. under about 3500 0t 3600 F. are to bemeasured a strip of tantalum is used as the heating element. It isnecessary that the atmosphere surrounding the tantalum strip at hightemperatures must be absolutel free from oxygen otherwise the tantalumwill be oxidized- If a high vacuum is obtained under the glass jar theatmosphere is safe enough to heat the tantalum. Of course, it is onlynecessary to use tantalum for very refractory materials which fuse abovethe melting temperature of platinum.

The temperature indicating device or galvanoineter may be calibrated bymelting various metallic pellets on the heating element in a well knownmanner. Thus, for

example, tin, zinc, copper, nickel, and other amaropriate metals may beused to calibrate the temperature scale 341-. l l hen the gal vanometer1S properly calibrated the improved apparatus gives extremely accurateresults which can be reproduced by the .san e or different observerswithin a remarl ablv close range. Of course, other materr such asnon-metallic substances may be u. c

in the calibration of the scale as one skilled 3 in the art will readilyunderstand.

In Fig. 8, has been depicted a modified cover for the envelopment of theheating element 1 of instrument 1. This cover conists of a metal shell15a which has a window opening 156 provided with a recess 150. Thisrecess is ground smoothly to provide a seat for window 15d which isfinely polished and made of a uniform thickness so that. it will notinterfere with the passage of light Then he continues to observe andheat radiations. Ordinarily the Window is only given-a frictional fit inthe window opening because the vacuum Will cause a tight joint to bemade. In some instances it may be well to seal the window in place byappropriate means such as by cementing with glycerine and litharge as isWell known.

It is to be observed that the invention provides a process and apparatuswhereby the fusing or melting point or temperature of refractory ornon-refractory materials can be very accurately observed Without theusual inconvenience, the elaborate apparatus required in the presentmethods of fusing or melting point determinations are eliminated, anaccurate and uniform temperature control and uniform temperatureincrease over a definite length of time can be ob tained, an accuratemeasurement of the temperature at which the fusion of the refrac' toryor non-refractory material takes place can be made, only very slightquantities of substances are required for the determination of thefusing or melting points of such substances, and the fusing or meltingpoints of a number of specimens may be determined simultaneously.

It is to be noted that the invention provides a process and an apparatuswhich eliminates a cumbersome gas furnace requiring a motor-drivenblower, the consumption of considerable volumes of gas and air andquantities of electricity, a large floor-space, the use of a separateroom required for a gas furnace liberating a large amount of heat, andthe difiiculty of fusing highly refractory ashes in a temperature beyond2800 F.

Claims:

1. In an apparatus for the determination of melting temperatures ofmaterials, the combination which comprises a container, means associatedwith said container for controlling the atmosphere therein, electricalmeans incorporated in said container for conductin electricity, saidmeans including a conductive element capable of being heated to meltingtemperature by electricity and of bearing specimens of materials to bemelted, a window provided in said container for observing a specimencarried on said conductive element, a pyromctcr focused through saidwindow on the specimen in the container, and a magnifier also focused onsaid specimen.

2. In an apparatus for the determination of melting temperatures ofmaterials, the combination which comprises an instrument forelectrically melting materials consisting of an electrical heatingelement enclosed in a container whose atmosphere can be controlled, anobservation Window in said container, and a pyrometer and telescopicmagnifier capable of being focused on said heating element; automaticmeans for controlling the electricity fiowing to the heating elementcontained in the said instrument; and a meter associated with thepyrometer for indicating the temperature of the heating element 3. In anapparatus for the determination of melting temperatures of materials,the combination which comprises an instrument for electrically meltingmaterials consisting of an electrical heating element enclosed in acontainer whose atmosphere can be con trolled, an observation window insaid container, and a pyrometer and telescopic magnifier capable ofbeing focused on said heating element; means for controlling the supplyof electricity to said heating element comprising a step-downtransformer, a rheostat having an automatically movable carriage, amotor operatively associated with said rlieostat for moving saidcarriage, and a switch for simultaneously controlling the electricityflowing to said transformer and to said motor; electrical connectionsbetween the secondary side of said transfornn er and the heating elementof said instrument for conducting'the electricity thereto; and a meterelectrically connected to the aforesaid pyrometer for automaticallyindicating the temperature of the heating element.

4. In an apparatus for the determination of melting temperatures ofmaterials, the combination which comprises an instrument forelectrically melting materials including a pyrometer and a telescopicmagnifier capabale of being focused on a specimen of the materialsundergoing melting; means for controlling the supply of electricityflowing to said instrument consisting of means constituting a source ofelectricity, control means electricallyconnected with said source tovary the flow of electricity going to the instrument, means forautomatically operating said control means to cause a substantiallyuniform increase in the quantity of electricity going to the instrument,and means for switching the electricity on and off; and a meterelectrically connected to said instrument for indicating the temperatureof a specimen undergoing a determination.

5. The combination set forth in claim 3 in which the carriage issupported on a rod having threads of such a character that the carriageis moved twice as fast on the starting portion of the rheostat as on thefinishing portion. 7

6. An instrument for the determination of the melting temperatures ofmaterials comprising in combination a supporting frame and arm carryingtwo bracket-s, an insulating foundation secured to said supporting frameand having electrical and gas connections incorporated therein, anelectrical heating element mounted on said foundation and connected tosaid electrical connections, a refractory cover seated in a channel insaid foundation so as to enclose said heating element said cover havingan observation window, a gasket fitted in said channel under the edge ofsaid cover and adapt ed to make a gas-tight joint, a pyrometer a windowina metallic shell whereby black body temperatures are approximated inthe space under the cover.

8; The process of determining the melting temperatures of materialswhich comprises establishing a chamber Within which black bodyconditions are approximated, heating a surface supporting a specimen ofthe material whose melting temperature is to be determined within theaforesaid chamber, automatically regulating the heating of the saidsurface and specimen to increase the temperature thereof at asubstantially definite rate within a given restricted time limit, continuing the application of heat to cause the melting of the specimen ofmaterial under determination, maintaining an element thermally sensitiveto the radiations emitted by said specimen and heated surface withinsuch a range of the latter that the radiant energy emitted from theheated surface is effective thereon, and measuring the temperature atwhich said specimen melts with the aid of said thermally sensitiveelement,

9. The proce s of determining the melting temperatures of materialswhich comprises establishing a chamber within which black bodyconditions are approximated, causing electricity to How through ametallic strip supporting a specimen of the material whose meltingtemperature is to be determined Within the aforesaid chamber,automatically controlling the electricity flowing through said strip toincrease the temperature thereof at a substantially definite rate withina. given restricted time limit, continuing the application of heattocause the melting of the specimen of material under determination,maintaining an element thermally sensitive to the radiations emitted byI said specimen and heated surface Within such a range of the latterthat the radiantv energy emitted from the heated surface is eflectivethereon, and measuring the tem-.

perature at which said specimen melts with the aid of said thermallysensitive element.

10. The process as set forth in claim 8 in Which the increased'heatingis temporarily discontinued during the step of measuring the meltingtemperature of the specimen. In testimony whereof I have hereunto set myhand.

LEA FRANK DE GRAAF, Ewecutrz'm 0f Garret A. (Z0 Gmaf, deceased.

